The machining of metalwork by a machinist using his machine tools generally involves cutting, drilling and shaping of a piece of metal stock to precise measurements of the final product. Finding the exact location of the edges of a workpiece is difficult for any machinist, especially since these edges, lines, axes and, in general, datum points must be determined often within an 0.0005 inch accuracy. Many indicating tools, center finding devices, and edge locating instruments have been developed to help the machinist perform some of these determining tasks with more accuracy. There are static locator devices which incorporate an indicting light such as those devices of Mann disclosed in his U.S. Pat. No. 1,040,715 and of Pierce as disclosed in his U.S. Pat. No. 2,109,976 in which contact between a cylindrically shaped conductive locating portion of the locator device and the metal workpiece completes a circuit and illuminates a standard incandescent light bulb. Later Hopkins in his U.S. Pat. No. 3,499,226 disclosed his improved electrical connections between components in a static indicator which was lighted via energy of a battery and inserted into a chuck or the collet of a jig bore or milling machine.
In 1946, Samuel Simers in his U.S. Pat. No. 2,490,483 illustrated and described his dynamic locating device, which is a rotating tool with a flexibly attached tip, which upon contact with a workpiece turned on a standard light bulb receiving energy from a power source not contained within this rotating tool.
Simers' dynamic tool increased the accuracy and improved machining measurements by utilizing the concept of rotational eccentric to concentric alignment contact between a workpiece and the circumference of the concentric rotating tip of the locator tool.
However, the high degree of precision required for such work could still not be easily and quickly achieved because very accurate visual observation was required to determine at what precise location a light bulb was continuously on, i.e. continuous contact being made, rather than flickering, i.e. upon intermittent contact. Or as in Simers' locator tool, there was the very accurate visual observation to be made when the light bulb light had ceased completely, as the continuous contact between tip and workpiece caused an intentional short circuit.
These representative patents indicate there is still a need for quicker and more accurate determination of datum points by a machinist using a dynamic, reliable, impact resistant, compact, internally powered, light emitting, precision locator tool, which will be available at a reasonable cost.